The invention relates to a rotor spinning machine comprising a plurality of operating units situated next to each other. Each operating unit contains a spinning unit with a singling-out device having in its body a rotatably mounted combing roller. The combing roller is equipped on its circumferential surface with an operative coating. Around the combing roller there is, provided in the body of the singling-out device, a circumferential fibre channel. The coating""s operative section extends in the sense of rotation of the combing roller from the mouth of the sliver feeding device to the supply channel that brings the singled-out fibres into the rotor. The operative section of the circumferential fibre channel has a mouth of a closable supply channel for pressure air.
At each yarn interruption on each spinning unit in the rotor spinning machines, the spinning process is to be restarted by inserting the yarn end into the rotor of the spinning unit during yarn rupture or during the tube substitution for a fully wound bobbin. The yarn end receives fibres deposited in a well-known manner on the collection surface of the rotor. Continuous spinning restarts by the following yarn draw-off. This whole cycle is called spinning-in.
Rotor spinning machines for open-end spinning can be divided into machines depending on the method by which underpressure is generated in the rotor. One machine has an active rotor fitted with vent holes for generating the underpressure in the rotor by its own revolving motion on one side. Alternatively, machines with a passive rotor may be provided in which the underpressure is generated by seating the rotor in an underpressure chamber connected with an underpressure source on one side. While there are some mutual differences in the spinning-in operation, each of these machines keep their respective combing roller in uninterrupted rotation while the sliver feed is stopped. The rotating combing roller releases fibres from the sliver end or also tears off or breaks off parts of the sliver. This process goes on for a time interval lasting up to the arrival of an attending device or of the operator.
If the spinning-in operation is carried out automatically or manually by the attending device on a fibre band made of a damaged sliver end, the piecer quality is poor and the number of failed spinning-in attempts is high. Poor quality piecer reduces the yarn usefulness for further processing in the textile industry such as in weaving. This is because it leads to ruptures of the yarn being processed or to aesthetic defects of final products.
Patent CZ 280036 G6 discloses a method of spinning-in yarn on rotor spinning machines in which the interruption of the spinning process is followed by the stop of the sliver feeding into the singling-out device. The combing roller continues rotating and the rotor is stopped at least for a cleaning period. At the restart of the rotor, the rotor receives back the yarn end which is brought into contact with the fibre band in the process of formation. Before the rotor starts and at the latest simultaneously with the beginning of the sliver feed, the surface of the combing roller is exposed to the action of pressure air. This air acts in the direction of the combing roller rotation between the place of inlet of the sliver to the combing roller and the beginning of the supply channel for feeding singled-out fibres to the rotor. In this way, sliver fibres and stuck impurities are removed from the operative surface of the combing roller. The pressure air supply is then stopped and the singled-out fibres are supplied into the rotor in a manner known in the art.
The CZ 280036 G6 patent also discloses a device for carrying out the method for rotor spinning machines with active or passive rotors fitted with an attending device. Rotatably mounted in the body of the singling-out device of the rotor spinning machine is a combing roller around whose cylindrical surface is fitted with an operative coating. A circumferential fibre channel is provided and communicates with a supply channel for feeding singled-out fibres to the rotor. Related to the combing roller is a sliver feed device that interrupts the circumferential fibre channel around the combing roller. The end of a closable pressure air supply channel is introduced into this fibre transport channel. The inner space of the channel is closed by a back valve which is on the outer side of the body of the singling-out device. The valve is adapted for connection to the pressure air supply provided on the attending device. At least the end part of the pressure air supply that serves for the connection to the back valve is adjustably mounted on the attending device.
The drawback of this solution consists in high requirements imposed upon the precision of the stop of the attending device in front of the operating unit of the rotor spinning machine. Equally high requirements are imposed on the precision of the construction and adjustment of the motion path of the pressure air supply. Both are necessary to ensure that the end part always comes to sit exactly on the back valve of the operating unit to be attended. Failing this, the spinning-in either fails to take place or leads to such a poor piecer quality which renders necessary a repetition of the spinning-in process.
The present invention aims to simplify the action of the attending device in restarting the spinning process on an operating unit of a rotor spinning machine. The pressure air action is maintained on the surface of the combing roller prior to the rotor start, and at the latest simultaneously with the start of the sliver supply channel and the termination of the action of the pressure air stream after the removal of the damaged and shortened fibres of the sliver end away from the spinning rotor area.
Features and advantages of the invention will be set forth in part in the following description or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention provides for a rotor spinning machine that has a singling-out device which includes a body. The body defines a circumferential fibre channel and an auxiliary supply channel that is in communication with the circumferential fibre channel. The auxiliary supply channel may deliver cleaning pressurized air into the circumferential channel at selected times. A combing roller is rotatably mounted within the body. A closing device is in fluid communication with the auxiliary supply channel. An air pressure source is in fluid communication with the auxiliary supply channel through the closing device. Upon actuation of the closing device, it limits the pressurized air that is supplied to the circumferential fibre channel from the auxiliary supply channel. The air pressure source is in the rotor spinning machine and is in continuous communication with the closing device.
Also provided according to the present invention is a rotor spinning machine as previously discussed where the body defines a mouth for communication between the sliver feeding device and the circumferential fibre channel. The body defines a supply channel for communication between the circumferential fibre channel and a rotor. An auxiliary pressurized air supply channel is in communication with the circumferential fibre channel between the mouth and the supply channel. The combing roller may have an operative section on the circumferential surface of the combing roller.
The present invention also encompasses an embodiment of the rotor spinning machine as discussed above which further has a control unit that is used for controlling the closing device.
Another embodiment of the present invention exists in which the rotor spinning machine as discussed above has a closing device that is a valve.
The present invention also includes an embodiment of a rotor spinning machine as discussed above where a control unit may be in communication with an attending device. This communication occurs at least during the time period when the attending device is stopped in an attending position by an operating unit.
Alternatively, the present invention includes an embodiment of a rotor spinning machine as previously discussed where the air pressure source is in fluid communication with the closing device through a pressure hose.
Additionally, the present invention also includes an embodiment of a rotor spinning machine as previously discussed where the closing device has an electromagnetic valve.
Further embodiments are present and consist of combinations of the afore-mentioned features. Also, other embodiments are defined in the claims.